Method of making dentures



B. F. REGAN March 4, 1969 METHOD OF MAKING DENTURES Filed June 4, 1965 ZmL TA AT 5 Wm N x m FIE-.2

INVENTOR. BA ERIE F. REG/4N ATTORNE V5 United States Patent Office3,431,183 Patented Mar. 4, 1969 3,431,183 METHOD OF MAKING DENTURESBarrie F. Regan, 1760 Manor Drive, Hiilsborough, Calif. 94010 Filed June4, 1965, Ser. No. 461,455 US. Cl. 2044 5 Claims Int. Cl. C23b 7/00; A61c13/22 ABSTRACT OF THE DISCLOSURE A method of making dentures whichcomprises essentially electroforming three layers of metals on a replicaof the mouth with the first and third layers formed of a tissuecompatible metal and the intermediate layer formed of an unstressedmetal stronger than the tissue compatible metal. The electroformingoperation is interrupted to embed a bubble of stop-01f material in themetal backbone of the denture, and the bubble is subsequently opened andthe stop-off material removed to provide an anchor and parting line forgum replica material of the denture.

This invention relates to a method of manufacturing dentures and moreparticularly to a method of electroforming the metal portions ofdentures.

In the art of manufacturing dentures, a variety of techniques areemployed for producing a denture backbone which is the structuralcomponent of the denture which conforms in shape to the users mouth. Thedenture backbone is generally formed of a metal and carries a body ofmaterial which resembles the users gums and a line of artificial teethembedded in this body of material. The techniques employed heretoforefor manufacturing the backbone" involved the preparation of a replica ofthe users mouth by first casting an impression of the users mouth andthen making from the impression a mouth replica which is a body ofmaterial having the same surface as the patients mouth. In the priorpractices of forming the denture backbone, Various techniques, such ascasting and swaging, have been employed. When the backbone is formed bycasting or swaging in this way, the backbone generally does not fitexactly the contour of the users mouth either because of damage to themouth replica during manufacture or dimensional changes caused bythermal expansion or contraction of cast materials during themanufacturing process.

The technique of electroforming has been used in the past formanufacturing dental backbones as indicated by the following US.patents: 1,453,303, Yaryan; 1,612,605, Beunaventura; 2,335,774, Landry.

The electroforming methods employed in the past have provided certainadvantages in the making of metal backbones for dentures in that theseelectrodeposition methods eliminate dimensional changes in the metalbackbone caused by thermal expansion, wear on the mouth replica andcontraction of casting materials, but substantial problems have beenencountered with electroformed dentures. Thus, when the metal backboneof the denture is electroformed on the mouth replica, the metal backbonewill acquire the exact surface configuration of the users mouth, butlimitations have been encountered in the metal from which the backbonecan be made because the metal to be used must be carefully selected, andthe process of its electrodeposition must be carefully selected toprovide a metal which is unstressed. In this regard, the metal backboneof the denture is provided with large curved areas, and if the metal ofthe backbone is deposited under tension or compression, the stress ofthe metal will deform the metal backbone from its intendedconfiguration. For these reasons, the metal backbone is preferablyelectroformed from nickel or a nickel alloy which can be deposited in anunstressed condition and which provides sutficient strength for themetal backbone that it will not be bent or damaged in normal use ornormal servicing.

When the metal backbones for dentures have been electroformed fromnickel, they have been covered with another metal different from thenickel or nickel alloy to provide an exterior metal coating which iscompatible with body tissue and will not cause any undesirable taste inthe users mouth or irritation to the tissue of the users mouth. When thenickel backbone is covered with another metal in this way, difiicultiesare encountered in obtaining good electrical current distribution overthe metal backbone when the metal backbone is plated, and the beneficialcharacteristics of the metal backbone are destroyed because the layer ofmouth compatible metal which is plated on the metal backbone changes theconfiguration of the metal backbone to a sufiicient extent that it nolonger provides a perfect fit in the users mouth.

I have found that all of the above mentioned disadvantages of priormethods of making dentures can be overcome, and the metal backbones fordentures can be made with such exact conformity with the surface of theusers mouth that a hydraulic seal develops between the tissue of theusers mouth and the metal backbone where this hydraulic seal is sostrong that unusually good retention of dentures in the users mouth maybe obtained.

In accordance with this invention, the metal backbone of a denture ismade by electroforming on a replica of the mouth a first layer of metalwhich is compatible with bodytissue, thereafter electroforming on saidfirst layer a second layer of unstressed metal which is stronger thanthe metal of the first layer, thereafter electroforming a third layer ofmetal compatible with body tissue on top of the second layer, with thefirst and third layers generally made of the same metal, and thereafterremoving the composite layers of metal from the mouth replica. In thisway, a metal backbone for dentures is provided in which the surface ofthe backbone which contacts the users mouth tissue has the exact surfaceconformation of the surface of the mouth replica, and a strong metalbackbone having essentially the characteristics of unstressed metal isprovided while the surface of the metal in the backbone is compatiblewith the body tissue.

Additionally, I have found that the manufacture of the dentures may besimplified substantially by forming certain features of the backbonewhile the backbone is being electroformed. In this regard, metalattachments are often soldered to the metal backbone to provide afinishing line Where the plastic material representing the gum ends, andmetal attachments are also soldered to the backbone to lock the plasticmaterial onto the backbone and to form a postdam at the inner edge ofthe backbone. In accordance with this invention, the electroforming ofthe backbone may be interrupted and the partially formed backbonemodified so that these metal attachments are integrally formed with thebackbone as it is electroformed.

Other features and advantages of the invention will become apparent fromthe following description read in conjunction with the attached drawingsin which:

FIG. 1 is a perspective view of a denture made in accordance with themethod of the invention;

FIG. 2 is an exploded view of the denture of FIG. 1 illustrating thesequential method of manufacturing the backbone of the denture, and

FIG. 3 is a sectional view on an enlarged scale illustrating a detailedfeature of the backbone.

The mouth replica is prepared for electroforming in a manner known tothe art where for instance the mouth replica is first sealed with asolution of polyvinyl chloride then sensitized to render the replicaelectrically conductive by coating the replica with silver paint orchemically reducing a silver, copper or nickel layer on the surface andattaching the replica to the cathode of suitable electroformingapparatus. After the mouth replica is prepared for electroforming, alayer of tissue compatible metal is plated onto the replica, and thistissue compatible metal may be gold, rhodium, chromium, silver orplatinum, but gold is generally preferred. The first layer of tissuecompatible metal is formed in a thickness of about 0.0005 inch to about0.005 inch, but preferably less than 0.002 inch.

After the first layer of tissue compatible metal is formed, anintermediate layer (not shown on the drawings) may be formed if it isdesirable to reduce the thickness of the first layer and provide anintermediate layer of high hardness and thermal conductivity between thefirst layer and the central body layer of the backbone. Thisintermediate layer, if desired, may be in a tin nickel alloy formed of65 percent tin and 35 percent nickel.

After the first layer of tissue compatible metal has been formed, andafter any intermediate layer is formed, it it is desired, the centralbody portion of the metal backbone is electroformed as a second layer.This central second layer of the backbone is preferably formed ofunstressed nickel made for instance in accordance with the sulfamatenickel plating process, This second layer is formed in a sufiicientthickness, preferably about 0.015 inch, to provide substantial strengthand durability in the metal backbone.

After the second or central body layer of the metal backbone iselectroformed, an additional intermediate layer of silver or tin nickelmay be electroformed as mentioned above, and there after the backbone isready to receive its final or third layer.

The third layer is electroformed in the same way as the first layer andpreferably of the same tissue compatible metal, and after the thirdlayer is completed, the electroforming of the metal backbone isfinished. The metal layers homogeneously bonded to each other are thenremoved from the mouth replica in any convenient way, and the peripheraledge of the backbone may be trimmed to provide the exact size metalbackbone desired for the denture. If the backbone is trimmed after it isremoved from the electroforrning operations, the edges of theintermediate layers of the backbone should be masked at the edge of thebackbone, and this may be accomplished simply by masking the entiremetal backbone with a non-conductive material before the edge of thebackbone is trimmed and then electroplating a tissue compatible metalonto the backbone before the masking material is removed.

As indicated above, it is often desirable to provide modifications ofthe metal backbone at the finishing line, the postdam, and other pointson the backbone to which plastic material resembling the users gums willbe attached. These modifications may be accomplished most efiicientlyduring the electroforming of the metal backbone to eliminate additionalwork on the backbone after it is electroformed and to provide thesemodifications in a way where the plastic material of the denture will befirmly locked into the center nickel layer of the backbone.

Thus, FIG. 3 illustrates one technique which may be employed inaccordance with this invention for making the finishing line of thedenture Where the plastic material of the denture ends and a retentionbar which locks the plastic material onto the metal backbone. Thebackbone is provided with two continuous bubbles and 12 running aroundthe circumference of the backbone along the tooth receiving areathereof,,and the bubbles 10 and 12 are slotted at 14 and 16respectively. The slot 14 runs along the finishing line of the dentureso that when the plastic material 18 resembling the users gums isapplied to the denture, the plastic material 18 will penetrate into thebubbles 10 and 12 locking itself to the backbone, and the plasticmaterial 18 i appe r t9 en at the lidge of the slot 14 thereby defininga clean finishing line in the denture.

The bubbles 10 and 12 may be formed very efiiciently during theelectroforrning of the metal backbone by interrupting the electroformingof the central nickel layer when the central nickel layer has reachedapproximately onehalf of its intended thickness. Thus, the partiallyformed metal backbone may be removed from the electroforming apparatusafter the central nickel layer has been formed to a thickness of about0.007 inch, and a ribbon of wax may be applied around the inner andouter circumferences of the partially formed backbone in the areas whichthe bubbles 10 and 12 are to occupy. The top surface of the wax is thensensitized to conduct an electric current, and the partially formedmetal backbone is returned to the electroforming apparatus to completethe electroforming of the center nickel layer to its thickness of about0.015 inch.

Thereafter, the surfaces of the two bubbles 10 and 12 may be slottedwith a suitable knife or the like, and the wax in the bubbles may bedissolved or otherwise removed to leave hollow interior bubbles intowhich the plastic material 18 may be extruded when the denture isfinally made.

Other methods may be employed for modifying the backbone during theperiod when it is being formed. For instance, instead of forming theretention bar as a bubble 12, the formation of the bubble 12 may beeliminated, and instead, a series of holes may be drilled in the centralnickel layer after the central nickel layer is completed and before thethird layer of tissue compatible metal is applied. In this way, theelectroforming of the final tissue compatible layer will deposit tissuecompatible metal at the edges of the drilled holes without depositingsubstantial metal in the bottom of the holes. When the plastic material18 is later extruded into the holes, it will be effectively locked intothe holes by the converging side walls of the holes.

While one specific embodiment of the invention has been illustrated anddescribed in detail herein, it is obvious that many modificationsthereof may be made without departing from the spirit and scope of theinvention.

I claim:

1. The method of making a metal backbone of a denture which compriseselectroforming on a replica of the mouth a first layer of metal selectedfrom the class consisting of gold, silver, chromium, rhodium andplatinum, which is compatible with body tissue, thereafterelectroforming on said first layer a second layer of a substantiallyunstressed metal which is stronger than the metal of said first layer,thereafter electroforming a third layer of a metal compatible with bodytissue on top of said second layer, and thereafter removing said layersof metal from said replica.

2. The method of claim 1 characterized further by the inclusion of thesteps of: interrupting the electroforming of said second layer toproduce a partially formed metal backbone, modifying said partiallyformed metal backbone by applying a stop-off material thereto to preventfurther electroforming in a portion of the space adjacent to the surfaceof said partially formed metal backbone, resuming the electroforrning ofsaid second layer to complete said second layer with spaces thereinhaving side walls sloping toward each other and away from said firstlayer, and removing said stop-off material from said backbone.

3. The method of claim 1 characterized further by the inclusion of thesteps of: interrupting the electroforming of said second layer, applyingon top of the partially formed second layer and along the finishing lineof the denture backbone a continuous strip of a material different fromthe metal of said second layer, resuming the electroforming of saidsecond layer to complete said second layer with said strip of materialembedded therein, cutting a slot narrower than said strip of materialinto said 5 strip of material along the finishing line of the denturebackbone, and removing the strip of material from said metal backbone toleave a cavity in said second layer communicating with the finishingline.

4. The method of making a metal backbone of a denture provided withsurfiace modifications for attachment to denture material representinghuman gums which comprises: electroforming on a replica of the mouth alayer of metal, interrupting the electroforming of said layer of metalto produce a partially formed metal backbone of predetermined thickness,modifying said partially formed metal backbone by applying an electricalstopoif material thereto to prevent further electroformiug in a portionof the space adjacent to the surface of said partially formed metalbackbone, resuming the electroforming of said layer of metal, continuingto electroform said layer of metal until said backbone has a thicknessof at least about twice said predetermined thickness, and removing saidstop-off material from said backbone.

5. The method of making the metal backbone of a denture which compriseselectroforming a layer of metal on a replica of the month, interruptingthe electroforming of said layer to produce a partially formed metalbackbone of predetermined thickness, placing on the surface of saidpartially formed metal backbone in a local area thereof a body ofmaterial different from the electrodeposited metal in said partiallyformed b ckbone, resuming the electroforming of metal on top of saidpartially formed metal backbone and on top of said body of material andcontinuing said electroforrning until the thickness of said backbone isabout twice said predetermined thickness to produce a metal backbonecontaining a bubble filled With said body of material, opening saidbubble, and removing said body of material from said metal backbone.

References Cited UNITED STATES PATENTS 1,453,303 5/1923 Yaryan 204-42,335,774 11/1943 Landry 204--4 JOHN H. MACK, Primary Examiner.

T. TUFARIELLO, Assistant Examiner.

